It is proposed to undertake an experimental and theoretical study of dynamic anisotropic spin-spin exchange interactions. The primary area of study will be long range superexchange, since this type of exchange is sensitive to both static and dynamic effects related to the mechanisms of molecular interactions. The coupling of a transition metal atom to a near-by free radical is proposed as a unique problem with important implications for the theory of homolytic cleavage of the cobalt to carbon bond in coenzyme B12-enzyme-substrate reactions. Two biochemical systems of this type have recently been studied by the author in which it is shown that there is evidence for a novel dynamic exchange interaction and that useful chemical information i.e. the "magnetic geometry" of the complex, can be derived from the accurate physical analysis of the spin-spin interactions. EPR and magnetic susceptibility measurements are proposed for a number of metal-lig- and molecules and metalloproteins with measurable isotropic exchange and anisotropic exchange coupling using Jahn-Teller (vibronic) interaction theory, and the density matrix lineshape theory. The other goal is the general development of a semi-empirical Heitler-London treatment in an attempt to develop a semi-quantitative theory for the exchange interaction between a paramagnetic transition metal atom and anear-by free radical, and a extension of Moriya's rules. In addition, the general biochemical significance of the "magnetic geometry" concept will be investigated in model systems and in significant biochemical systems.